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4throck
Posted on: Jan 5 2017, 09:21 AM


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Some nice images on the arXiv PDF.
There's potential for a small animation there wink.gif
  Forum: Rosetta · Post Preview: #234031 · Replies: 1412 · Views: 668753

4throck
Posted on: Dec 18 2016, 05:38 PM


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I have a few more images I can add for completeness sake.
For example, this paper shows images 38 and 45:
http://eaps4.mit.edu/research/papers/Travis_etal_1979a.pdf

But again, the data if from early on the mission.
  Forum: Venus · Post Preview: #233795 · Replies: 8 · Views: 14393

4throck
Posted on: Dec 16 2016, 10:39 AM


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Just to say that I've updated my astronomy page and some links have changed.

The Pioneer Venus images are now displayed with image number, code and date.
Processing is minimal, just histogram equalization of the scans.

There are a few more Pioneer Venus images online, but I've been unable to identify them.

http://www.astrosurf.com/nunes/explor_pvenus.html
  Forum: Venus · Post Preview: #233765 · Replies: 8 · Views: 14393

4throck
Posted on: Dec 16 2016, 10:30 AM


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I think that the issues mentioned (jpg compression, limited dynamic, noise) may prevent identification of those "particles".
Even if they are real, the images may not have enough data to characterize what we are seeing.
  Forum: Titan · Post Preview: #233764 · Replies: 18 · Views: 10164

4throck
Posted on: Dec 13 2016, 04:04 PM


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The image sequence (in chronological order) shows the lander's light dimming as time passes and the battery runs out.
At least I remember reading something regarding the lamp Vs ambient light levels and that's the only noticeable change.

Here's an official release with all the data:
https://www.youtube.com/watch?v=sZC4u0clEc0

Once tried to use that difference in illumination to get some color, but that JPG compression is just too high.
An interesting processing would be to properly de-block the images (also for Pathfinder or Galileo).
  Forum: Titan · Post Preview: #233715 · Replies: 18 · Views: 10164

4throck
Posted on: May 27 2016, 01:43 PM


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QUOTE (JRehling @ May 26 2016, 07:50 PM) *
... I'm not sure I know of anyone else getting surface details with a telescope of this size.


That darker detail, so well centered on the disk, seems a bit like a processing artifact. Or your secondary mirror ;-)
Extreme processing on images so small (compared to the theoretical resolution) can be tricky.
The limb's contrast with the dark background can be enough to create a "doughnut" or ring effect.

But if you can get more images and do a rotation movie, I'd be convinced ;-)
  Forum: Jupiter · Post Preview: #230958 · Replies: 108 · Views: 102835

4throck
Posted on: Jul 31 2015, 02:13 PM


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Updated highres CIVA images published here:
http://www.esa.int/spaceinimages/Images/2015/07
  Forum: Rosetta · Post Preview: #224983 · Replies: 1412 · Views: 668753

4throck
Posted on: Jul 31 2015, 02:06 PM


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QUOTE (scalbers @ Jul 30 2015, 09:59 PM) *
Just a little cleanup for my Pluto map:


Great work as always!
Any chance of filling the bottom of the map with Hubble / occultation data ?

  Forum: New Horizons · Post Preview: #224982 · Replies: 79 · Views: 68014

4throck
Posted on: Jul 27 2015, 04:03 PM


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Left: generated noise
Right: wild processing of the generated noise

Attached Image


If you want to find it, a pattern always emerges. On this case, I tried to bring out "linear features" and behold they appear. I can make out a diagonal line across the top left half!
If I started with a more complex image (with larger scale shadings for example) the resulting features would also be more elaborate.

JPG compression artifacts, aliasing effects on scaling our even histogram manipulation will all generate noise.
Just like Phil exemplified.

The purpose of image processing is to remove or hide the noise, not to amplify it!


To compare NH to HST, the first step it to reduce NH data to the same resolution as HST, and not the other way around.

You get this (NH at bottom):
Attached Image


Reasonable match to the top HST map, given that the wavelengths and phase angles are different.
  Forum: Image Processing Techniques · Post Preview: #224841 · Replies: 31 · Views: 11223

4throck
Posted on: Jul 24 2015, 01:52 AM


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Agreed.
In theory it works, in practice you'd need to calibrate the images (flat field, linearize the response, etc, etc).

(Violet is always a tricky filter to deal with, since it should translate to both the Red and Blue channels. But that's really Voyager related so let's not discuss it here ;-) )
  Forum: New Horizons · Post Preview: #224607 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 23 2015, 11:57 PM


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QUOTE (ZLD @ Jul 23 2015, 10:45 PM) *
I took the latest MVIC image, subtracted out all of the filtered color to obtain a green channel.


My suggestion to get a green channel with real data would be to use the panchromatic image (Lorri).
That one is the sum of all wavelength (of course, subject to the camera's response).
To keep it simple, let's say that Lorri = R+G+B
You add R + B from MVIC, convert to grayscale and subtract it from Lorri.
You get G.

(In theory you can use a similar tick to get red from Voyager's Violet and Orange channels....)

The only trouble is that you need perfect registration and to compensate for camera response. rolleyes.gif
  Forum: New Horizons · Post Preview: #224601 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 23 2015, 08:41 PM


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QUOTE (fredk @ Jul 23 2015, 06:20 PM) *
What did you do for the green channel, 4throck?


Green = 50% Red + 50% Blue laugh.gif
  Forum: New Horizons · Post Preview: #224580 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 23 2015, 05:14 PM


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Real color (no IR data) and gamma change to a more natural value:

Attached Image

  Forum: New Horizons · Post Preview: #224561 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 18 2015, 10:43 PM


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My reprojection of the false color images over the Lorri images:

Attached Image

Attached Image

  Forum: New Horizons · Post Preview: #224184 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 17 2015, 01:28 AM


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About the shadows, we don't know if they are projected into flat ground.
If not, the shadows will look distorted, tilted, broken, etc.
  Forum: New Horizons · Post Preview: #223883 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 17 2015, 12:04 AM


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I've uploaded an improved image.

Since I've added noise, the SN in the image is lower. I'd be extra cautious with any small details there.
The noise helps to mask the blocks, so that your brain is no longer distracted by them. But it can also "connect the dots" and create false details.
  Forum: New Horizons · Post Preview: #223874 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 16 2015, 11:52 PM


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Here's the Charon terminator strip with added noise, slightly blurred and level adjusted.

Attached Image

  Forum: New Horizons · Post Preview: #223870 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 15 2015, 11:30 PM


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One thing that works for me with heavily compressed images is to add some noise.
That gets rid of the block artifacts and for some reason the entire image becomes more "readable".
Surely just a perception thing, but for me it helps.

Here's Charon "noised":

Attached Image
  Forum: New Horizons · Post Preview: #223677 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 15 2015, 11:09 PM


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Trying to match the high-res image with the full disk view, I get this:

Attached Image
  Forum: New Horizons · Post Preview: #223674 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 14 2015, 11:51 PM


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Guessing that the color image is IR R B , I've processed it as R (G=0.5R+.5B) B and I get this:

Attached Image


Levels adjusted so that brightest ices are white. Certainly looks less psychedelic!
  Forum: New Horizons · Post Preview: #223403 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 14 2015, 05:30 PM


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QUOTE (Bjorn Jonsson @ Jul 14 2015, 06:08 PM) *
..it seems that the image was in fact colorized using higher resolution MVIC data than we have been seeing until now...


Second that, there's some saturation variation and if you stretch the levels you get some white/pink areas related to different terrains.
  Forum: New Horizons · Post Preview: #223325 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 14 2015, 03:46 PM


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Yes, doubtful.

Highpass will bring out ring artifacts, and create the illusion of a brightness along the limb.

On the other hand, the released image is not raw.
Certainly there was a circular selection made around the planet, to bring the lightness of the disk up, while keeping the background of the frame black.
Makes perfect sense for them to do that on an image that most people will see on TV, cellphone, etc, in well lit places.
So it's that selection that you are seeing, not the atmosphere. At least that's my interpretation.
  Forum: New Horizons · Post Preview: #223304 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 14 2015, 02:55 PM


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High passed and level streched !

Attached Image
  Forum: New Horizons · Post Preview: #223289 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 14 2015, 11:30 AM


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Looks like a filled depression...
  Forum: New Horizons · Post Preview: #223219 · Replies: 1286 · Views: 450726

4throck
Posted on: Jul 11 2015, 12:26 AM


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I've maked some of the circular areas. The pattern is not too different from the "hexagonal" terrain... interesting!

Attached Image



Speculation: The northern hemisphere is covered by a uniform polar cap.
On the tropical zones we start to see the underlying darker terrain (dunes, degraded craters, faults, etc).
  Forum: New Horizons · Post Preview: #222719 · Replies: 729 · Views: 296788

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